Chris Urmson, director of Google's Self-Driving Car Project, said that there is "a space for passengers' belongings, buttons to start and stop and a screen that shows the route - and that's about it."

The car's top speed is about 40 kilometres per hour.

A Google promo video on YouTube shows elderly passengers praising how the car slows down as it approaches a bend in the road before accelerating. A blind passenger also describes wanting a self-driving car.

Google said it plans to build about 100 prototype vehicles and will test-drive models with manual controls this summer. The company wants to run a small pilot program in California in the next few years. It did not indicate whether it would manufacture the car or work with carmakers to get them on the road.

It did not give a possible price for future production models of the car.

The prototype comes after years of research by Google into automated driving technologies, including thousands of kilometres of tests drives on highways and city roads.

It believes self-driving cars that will detect and avoid vehicles as well as pedestrians, cyclists and other potential hazards on the road can make driving safer.

Under May 2014 California regulations, testing of autonomous vehicles must be performed with test drivers in the vehicle's driver seat who can immediately take control. The state is developing regulations for public operation of self-driving cars, and the rules are expected to be adopted by Jan. 1, 2015.